Method and apparatus of symmetrically chamfering substrate

ABSTRACT

A method of symmetrically chamfering a substrate includes repeating, at least a plurality of times, the steps of chamfering an edge of the substrate using a chamfering wheel, measuring an asymmetric chamfering deviation (y) of the edge of the substrate which is chamfered, and controlling a relative position of the chamfering wheel with respect to the substrate by a value of a function f(y) of the variable y. It is possible to constantly symmetrically chamfer the edge of the substrate via active response to a change in the chamfering environment without a hardware-based operation of the related art.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Korean Patent Application Number 10-2013-0060306 filed on May 28, 2013, the entire contents of which are incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus of symmetrically chamfering a substrate, and more particularly, to a method and apparatus of symmetrically chamfering a substrate by measuring an asymmetric chamfering deviation of the substrate and controlling the position of a chamfering wheel based on the asymmetric chamfering deviation.

2. Description of Related Art

In a plurality of fields, the edges of substrates are required to be chamfered. For instance, glass substrates which are used for flat panel displays, such as a liquid crystal display (LCD), a plasma display panel (PDP) and an electroluminescent (LE) display, can be manufactured by melting, shaping, cutting and chamfering processes. That is, it is possible to manufacture a glass substrate by melting a glass raw material, shaping molten glass into a plate by solidifying it, cutting the glass plate according to a predetermined size, and chamfering edges of the cut glass.

FIG. 1 is a schematic view showing the process of chamfering an edge of a substrate 10, and FIG. 2 is a side cross-sectional view showing the edge of the substrate 10 which is asymmetrically chamfered.

The edge of the substrate 10 is chamfered in the state in which the substrate is placed on a chamfering table 30. Here, it is preferred that the edge of the substrate be chamfered symmetrically in the top-bottom direction. However, since a glass substrate used, for example, for a PDP is thin (with a thickness of about 1 mm or less), a localized misalignment occurs between the center point of the cross-section at the edge of the substrate and the center point of a chamfering wheel 20 when the chamfering table is not flat or due to movement in the up and down direction during carriage of the chamfering table. In this case, the cross-section of the edge is ground more deeply at one side, such that the chamfered width of the upper surface differs from the chamfered width of the undersurface. This consequently forms an asymmetrically-chamfered point on the edge of the substrate, i.e. a localized area which is asymmetrically chamfered.

Traditionally, when the substrate is asymmetrically chamfered, an operation of replacing a component of a device which fixes the asymmetrically-chamfered portion of the substrate or precisely adjusting the local height of the chamfering table using a thin steel piece is carried out. However, this operation requires a process of stopping the chamfering of the substrate and disassembling, reassembling and precisely compensating the table, thereby causing massive damage to productivity. This also has the problem of the increased cost due to the replacement of the component.

The information disclosed in the Background of the Invention section is only for better understanding of the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.

BRIEF SUMMARY OF THE INVENTION

Various aspects of the present invention provide a method and apparatus of symmetrically chamfering a substrate, which enables an edge of the substrate to be constantly symmetrically chamfered via active response to a change in the chamfering environment without a hardware-based operation of the related art.

In an aspect of the present invention, provided is a method of symmetrically chamfering a substrate. The method includes repeating, at least a plurality of times, the following steps of: chamfering an edge of the substrate using a chamfering wheel; measuring an asymmetric chamfering deviation (y) of the edge of the substrate which is chamfered; and controlling a relative position of the chamfering wheel with respect to the substrate by a value of a function f(y) of the variable y.

In another aspect of the present invention, provided is an apparatus for symmetrically chamfering a substrate that includes a chamfering wheel which chamfers an edge of the substrate at least a plurality of times; a measuring part which measures an asymmetric chamfering deviation (y) of the edge of the substrate which is chamfered; and a controller which controls the relative position of the chamfering wheel with respect to the substrate by a value of a function f(y) of the variable y.

According to embodiments of the invention, it is possible to produce a symmetrically chamfered cross-section by automatically and constantly aligning the height of the chamfering wheel with the center point of the cross-section of the edge of the substrate by replacing the method of the related art in which the center point of the cross-section at the edge of the substrate is aligned with the center point of the chamfering wheel by compensating a chamfering table on which the chamfering operation is carried out. That is, the present invention has an effect in that the edge of the substrate can be constantly symmetrically chamfered via active response to a change in the chamfering environment without the hardware-based operation of the related art. In particular, the invention makes it possible to promptly determine the degree of deterioration of the chamfering table which is continuously deteriorated by the repeated chamfering operation, and to directly take necessary measures.

In addition, the invention does not require stopping the chamfering operation, and thus has an effect in that the edge of the substrate can be symmetrically chamfered in a simple way without sacrificing productivity.

Furthermore, the invention excludes labor and time loss which are required for the compensation of the chamfering table in the related art, thereby improving the efficiency of the chamfering process. That is, it is possible to obtain the maximum effect and significantly increase the level of distribution of the chamfered width while minimizing the load of the operation. It is also possible to mass-produce chamfered substrates while maintaining the difference between the chamfered widths of the upper surface and undersurface of the substrate to a maximum of 30 μm or less (an average level of 20 μm) by operating a simple program when a worker on duty is not carrying out the operation. The symmetry of chamfering was greatly improved over the compensation technique of the related art from which the symmetry having a difference between the chamfered widths of 50 μm or less cannot be obtained

The technique of measuring and compensating the degree of flatness of the chamfering table of the related art requires stopping the production line, and is a dangerous operation which must be carried out in the middle of equipment. In contrast, the invention can protect a worker from a dangerous environment.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from, or are set forth in greater detail in the accompanying drawings, which are incorporated herein, and in the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the process of chamfering an edge of a substrate;

FIG. 2 is a side cross-sectional view showing the edge of the substrate which is asymmetrically chamfered;

FIG. 3 is a flow diagram depicting a method of symmetrically chamfering a substrate according to an embodiment of the invention;

FIG. 4 is a schematic view showing a plurality of measuring points on the edges of a substrate;

FIG. 5 is a side cross-sectional view showing an asymmetric chamfering deviation on one edge of a substrate;

FIG. 6 is a view showing the chamfered width at the upper surface and the chamfered width at the undersurface at each chamfering which is carried out by a method of symmetrically chamfering a substrate according an embodiment of the invention;

FIG. 7 is a view showing the chamfered width at the upper surface, the chamfered width at the undersurface and an asymmetric chamfering deviation before and after a substrate is symmetrically chamfered by the method of symmetrically chamfering a substrate according an embodiment of the invention;

FIG. 8 is a view showing a decrease in the asymmetric chamfering deviation before and after the method of symmetrically chamfering a substrate according an embodiment of the invention is applied; and

FIG. 9 is a schematic view showing an apparatus of symmetrically chamfering a substrate according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below, so that a person having ordinary skill in the art to which the present invention relates can easily put the present invention into practice.

Throughout this document, reference should be made to the drawings, in which the same reference numerals and signs are used throughout the different drawings to designate the same or similar components. In the following description of the present invention, detailed descriptions of known functions and components incorporated herein will be omitted when they may make the subject matter of the present invention unclear.

FIG. 3 is a flow diagram depicting a method of symmetrically chamfering a substrate according to an embodiment of the invention, FIG. 4 is a schematic view showing a plurality of measuring points on the edges of a substrate, and FIG. 5 is a side cross-sectional view showing an asymmetric chamfering deviation on one edge of a substrate.

The method of symmetrically chamfering a substrate according to the invention repeats a chamfering step, a measuring step and a controlling step at least a plurality of times.

At the chamfering step, an edge of the substrate is chamfered using a chamfering wheel.

The substrate 10 is placed on a chamfering table 30. Herein, the terms “up (upward),” “down (downward),” “left” and “right” are used to describe the positional relationship but not to indicate the absolute position with respect to the surface of the earth. Therefore, the description that the substrate 10 is positioned on or above the chamfering table 30 merely means that the substrate 10 is positioned in a direction that is designated to be upward from the chamfering table 30, but the upward direction does not necessarily indicate that it faces away from the surface of the earth. While the substrate 10 may be a glass substrate for a display device, the invention is not limited thereto. The substrate 10 according to the invention can be made of any material as long as the substrate is supposed to be chamfered.

The chamfering wheel 20 is made of a material that is more rigid than the substrate 10. When the object to be chamfered is the glass substrate 10, the chamfering wheel 20 typically contains diamond grinding chips. In general, the chamfering wheel 20 is provided as a disk type. Concave grooves are formed in the outer circumference of the chamfering wheel 20 along the circumferential direction thereof. The inner sides of the grooves abut against the edge of the substrate 10, thereby evenly chamfering the edge of the substrate 10. The chamfering wheel 20 is grasped by a dedicated grinding machine and is thereby rotated at a high speed.

In general, the substrate 10 is moved and the chamfering wheel 20 is rotated in position. However, this is not always required. For instance, the arrangement in which the substrate 10 is fixed and the chamfering wheel 20 is movable is possible, or the arrangement in which both the substrate 10 and the chamfering wheel 20 are movable is possible. In response to the relative movement between the substrate 10 and the chamfering wheel 20, the chamfering wheel 20 chamfers the edge of the substrate 10 while moving along the edge.

At the measuring step, an asymmetric chamfering deviation (y) of the edge of the substrate is measured.

According to an exemplary embodiment, the asymmetric chamfering deviation is measured from the difference between the widths of the upper surface and the undersurface of the chamfered substrate 10. However, the present invention is not limited thereto. For instance, it is possible to measure the asymmetric chamfering deviation by directly inspecting the cross-section of the edge of the substrate 10 from the side. A variety of devices, such as a vision camera and a distance sensor, can be used to measure the asymmetric chamfering deviation.

It is preferred that an asymmetric chamfering deviation is measured from each of a plurality of points on the edge of the substrate. While FIG. 4 shows that this measuring operation is carried out on all of four edges, this is not intended to be limiting. Only a limited number of edges can be measured as required. For example, four vision cameras can be used in order to measuring the four edges of the substrate.

At the controlling step, the relative position of the chamfering wheel with respect to the substrate is controlled by the value of a function f(y), where the variable y is the asymmetric chamfering deviation.

Typically, the position of the chamfering wheel that is to be controlled is the relative height of the chamfering wheel with respect to the substrate. As described above, it should be understood that the term “height” is used in order to describe the relative positional relationship but not to indicate the absolute position. In addition, while the relative position may be changed by moving the chamfering wheel up and/or down, this is not intended to be limiting. For instance, it is possible to move the substrate in the up and down direction while fixing the chamfering wheel, or to move both the chamfering wheel and the substrate.

For instance, since a glass plate is thin (with a thickness of about 1 mm or less), it is bent along the shape of the upper surface of the chamfering table due to the flatness of the chamfering table and under the influence of the weight of the glass plate. In that state, the glass plate closely adjoins the upper surface of the chamfering table. Therefore, when the chamfering table 30 is not flat, the center point of the cross-section at the edge of the substrate 10 is locally misaligned from the center point of the chamfering wheel 20. When the height of a localized area of the chamfering table 30 is lower than a reference height, the center point of the edge of the substrate 10 is positioned lower than the center point of the chamfering wheel 20, as shown in FIG. 5. In this case, the undersurface of the substrate is more chamfered than the upper surface of the substrate, such that the chamfered width of the undersurface becomes greater than the chamfered width of the upper surface. Accordingly, the relative height of the chamfering wheel with respect to the substrate is controlled in the upward direction.

In contrast, when the local height of the chamfering table 30 is greater than the reference height, the local center point of the cross-section at the edge of the substrate 10 is positioned higher than the center point of the chamfering wheel 20. In this case, the upper surface of the substrate is more chamfered than the undersurface of the substrate, such that the chamfered width of the upper surface becomes greater than the chamfered width of the undersurface. Accordingly, the relative height of the chamfering wheel with respect to the substrate is controlled in the downward direction.

It is preferred that the controlling step individually controls the positions of the chamfering wheel when chamfering a plurality of points on the edge of the substrate, like the measuring step. While FIG. 6 and FIG. 7 show that this controlling operation is carried out on all of the four edges, this is not intended to be limiting. The controlling operation can be carried out on only a limited number of edges as required. For example, four chamfering wheels can be used in order to chamfer the four edges of the substrate.

After the relative position of the chamfering wheel 20 with respect to the substrate 10 is changed, the foregoing steps, including the chamfering step, the measuring step and the controlling steps, are repeated. While the edge of the same substrate 10 can be chamfered and measured again, it is preferable to use another substrate 10. That is, it is possible to chamfer and measure the edge of a plurality of substrates 10 while controlling the relative position of a single chamfering wheel 20 with respect to each of the substrates 10.

The number of repetitions can be designated in advance and inputted into a program, or the process can be repeated until the asymmetric chamfering deviation (y) has a value within a designated range. Furthermore, the measuring and controlling steps can be constantly carried out, i.e. limitlessly repeated, during the chamfering operation.

After the chamfering step, the degree of asymmetry of the cross-section at the edge of the substrate is measured, the asymmetric chamfering deviation is fed back, an amount of control f(y) (e.g. f(y)=y*a) is generated by multiplying the deviation (y) with a predetermined constant (a), and the height of the chamfering wheel is precisely determined by the amount of control. After this first cycle, the degree of asymmetry at the same point is measured, an amount of control is generated in the same way, and the position of the chamfering wheel that was previously set is corrected by accumulating this amount of control. When this series of processes is continuously repeated, a deviation in the chamfered width which is continuously changed due to the precision of carriage caused by deterioration of the chamfering operation and due to the flatness can be set to a minimum value.

FIG. 6 is a view showing the chamfered width at the upper surface and the chamfered width at the undersurface at each chamfering which is carried out by a method of symmetrically chamfering a substrate according an embodiment of the invention, FIG. 7 is a view showing the chamfered width at the upper surface, the chamfered width at the undersurface and an asymmetric chamfering deviation before and after a substrate is symmetrically chamfered by the method of symmetrically chamfering a substrate according an embodiment of the invention, and FIG. 8 is a view showing a decrease in the asymmetric chamfering deviation before and after the method of symmetrically chamfering a substrate according an embodiment of the invention is applied.

As shown in the figures, it can be appreciated that symmetric chamfering on an edge of a substrate was realized by repeating the chamfering, measuring and controlling steps only several times when the method of symmetrically chamfering a substrate according to the invention is applied. As the result of the operation carried out, it was possible to reach a desired level of about 50 μm (an average level of 20 μm) by carrying out the operation 5 times or fewer.

FIG. 9 is a schematic view showing an apparatus of symmetrically chamfering a substrate according to an embodiment of the invention.

As shown in FIG. 9, the apparatus of symmetrically chamfering a substrate according to an embodiment of the invention includes a chamfering wheel, a measuring unit and a controller.

The measuring unit measures an asymmetric chamfering deviation (y) of an edge of a substrate which is chamfered. The controller controls the position of the chamfering wheel by a function f(y), where the variable y is the asymmetric chamfering deviation.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented with respect to the drawings. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible for a person having ordinary skill in the art in light of the above teachings.

It is intended therefore that the scope of the invention not be limited to the foregoing embodiments, but be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. A method of symmetrically chamfering a substrate, comprising repeating cycles a plurality of times, each cycle comprising: chamfering an edge of the substrate using a chamfering wheel; measuring an asymmetric chamfering deviation (y) of the edge of the substrate which is chamfered; and controlling a relative position of the chamfering wheel with respect to a position of the substrate by a value of a predetermined function f(y) of the variable y.
 2. The method of claim 1, wherein the asymmetric chamfering deviation is a difference between a chamfered width of an upper surface of the substrate and a chamfered width of an undersurface of the substrate.
 3. The method of claim 2, wherein the relative position of the chamfering wheel is controlled to move upward when the chamfered width of the upper surface of the substrate is greater than the chamfered width of the undersurface of the substrate, and the relative position of the chamfering wheel is controlled to move downward when the chamfered width of the upper surface of the substrate is smaller than the chamfered width of the undersurface of the substrate.
 4. The method of claim 1, wherein the relative position of the chamfering wheel is a relative height of the chamfering wheel with respect to a height of the substrate.
 5. The method of claim 1, wherein the value of the function f(y) is obtained by multiplying the asymmetric chamfering deviation (y) by a predetermined control constant.
 6. The method of claim 1, wherein different substrates are chamfered in the respective cycles.
 7. The method of claim 1, wherein in each cycles, a plurality of the asymmetric chamfering deviations are measured at a plurality of points respectively on the edge of the substrate; and a plurality of the relative positions of the chamfering wheel are controlled when chamfering at the plurality of the points on the edge of the substrate.
 8. The method of claim 1, wherein the substrate comprises a glass substrate for a display.
 9. The method of claim 1, wherein the chamfering wheel has a concave groove in an outer surface of the chamfering wheel along a circumferential direction thereof.
 10. The method of claim 1, wherein measuring the asymmetric chamfering deviation (y) comprises measuring the asymmetric chamfering deviation (y) using a vision camera which detects a chamfered width of an upper surface of the substrate and a chamfered width of an undersurface of the substrate. 